2 answers

That is a link to the Assistant tooling with your workspace id. So even if it was working, only you should be able to get in. As you can’t, and I am assuming that it is one of your workspaces, then it looks like the instance of the tooling running in the UK region is down.

You will need to raise a ticket on IBM Cloud.

The tooling is an app that makes use of the Watson Service. If you can interact with your workspace though Slack then the Assistant service is running. Which also means that you could make workspace modifications through the API.